1. Field of the Invention
The present invention relates to an antiglare antireflective film, and to a polarizing plate and a liquid crystal display each using such a film.
2. Description of Related Art
Antiglare films can be broadly divided into two groups: antiglare films having a surface scattering quality in a substantial sense and those having both surface scattering and internal scattering qualities. In a display, such as CRT, a plasma display panel (PDP), an electroluminescent display (ELD) and a liquid crystal display (LCD), an antiglare film is generally placed at the topmost surface of the display for the purpose of avoiding formation of reflected images by reflection of extraneous light.
With the recent trend moving notably toward higher-definition displays, the arts of antiglare films having internal scattering quality higher than usual in addition to surface scattering quality are disclosed in Japanese Patent No. 3507719 as measures to improve minute unevenness in brightness (referred to as “glare”).
On the other hand, the art of scattering film which improves viewing angle characteristics of LCDs by not having surface scattering quality but having internal scattering quality alone is disclosed. In addition, it is known that films having both light scattering quality and an antireflective function in having effect on inhibition of surface reflection of extraneous light in a bright room are favorable when light scattering films are used at the topmost surfaces of displays.
Recent years have seen fast growth in the market of applications for viewing of big-screen displays, notably liquid crystal TV sets, from relatively distant positions. In such applications, the glare problem is relieved because the pixel size becomes larger as far as the definition is the same, and besides, the distances from viewers to displays become greater. Although the antiglare films having high internal scattering quality, which have been widely used as antiglare measures, have been used in those applications also, the high internal scattering quality causes a problem of lowering the resolutions of images (referred to as image blur), so the use of antiglare films is not always suitable for those applications.
For avoiding formation of reflected images by reflection of extraneous light, it is common to take a measure that the film surface is rendered uneven to blur the outlines of reflected images. By this measure, visibility from the direction of regular reflection of extraneous light is improved. When viewed from directions other than that of the regular reflection, however, black images take on whitish looks (referred to as white blur) because the diffraction of scattered light occurs in those directions. As attack on this problem, attempts to optimize the surface roughness and tilt angles at the film surface have been made. However, certain of those attempts (JP-A-2002-23870 and JP-A-2003-107205) are insufficient for performance improvements in all directions, and raise issues of productivity and cost.
For total performance improvement of a display unit, it is extremely important to optimize properties of an antiglare antireflective film after considering the viewing angle dependence of the display itself, such as a liquid crystal display.
As mentioned above, it is the present situation that any antiglare antireflective film having satisfying antiglare quality and ensuring satisfactory improvements in image blur and white blur at the same time is not proposed.